Having been in and out a bunch over the last year and going through way too much data before getting ADSL put into my Cambo place I have had a good chance to test out a few different companies. Having data is generally a huge saving as between skype and whatsapp etc the credit in SMS and voice calls lasts so much longer.

While Smart is cheaper, it had far less coverage, and cellcard has a good network but cost much more in data use.. so as far as I found the 'best' solution for working country wide with a cellphone and 3G data as far as my testing went is Metfone.

Be aware that the cheap looking 'unlimited' packages (bandwidth) throttle the 3G down to 256 or (claimed) 512 kbps after the first few gigs.. I found these throttled speeds to be truly awful and while they would get a text email or something couldnt skype with any reliability. They also seemed to cut out much more and generally be a paid in the arse.

Also be aware they offer fast 3G data packages designed to work with a dongle, but offer no voice capability on those. So useless for smartfone use but OK for a tablet From memory these where the 'UT' offerings.

The 2 packages I found most reliable are the LT12 and LT20 (I heard they did away with this last best one a couple of months ago) which gives 4 gig for 12 bucks and and 12 gig for 20 USD respectively in one month period. These packages are 'unlimited bandwidth' so not throttled and I have been getting 3 - 6 Mbit speeds on them in PP and not much less even in the country. Fast enough for skype, some small photos, media etc.

If you burn through the 4G of an LT12 in under a month, you can get another 4gig (for another 12 bucks) by resetting the package to a basic per byte cost (MI0 package) and then LT12 again. Your allowed 2 changes per month so this works one time, after that your stuck with pretty high per byte fees. The measured download accounts ran so much faster than the unlimited bandwidth offerings that it was worth the hassle.

The small phone shops of course have top up credit all over the country and most will have SIMs but tend to try tricks like overcharging for special offer sims or telling you that included credit on the SIM is an extra cost. A SIM is from memory 3 bucks and a 'good' cellphone shop should know all the codes to turn on 3G and set up a smartphone on the above LT packages, but if you want the easiest experience go direct to the metphone shop near riverside which is (if memory serves it might be one block to the south of this marker) here. http://goo.gl/maps/A7EeT